arm: kirkwood: Dreamplug : Use Marvell uclass mvgbe and PHY driver for Ethernet

The Globalscale Technologies Dreamplug board has the network chip
Marvell 88E1116R. Use uclass mvgbe and the compatible driver M88E1310
driver to bring up Ethernet.

- Currently, CONFIG_RESET_PHY_R symbol is used in
arch/arm/mach-kirkwood/include/mach/config.h for all Kirkwood
boards with mv8831116 PHY, with each board defines the function
reset_phy(). Undefine it for this board.
- Add board_eth_init() to use uclass mvgbe to bring up both network
port 0 and 1. And remove ad-hoc code.
- Enable CONFIG_PHY_MARVELL to properly configure the network.
- Add myself as maintainer (this board seems to be orphaned,
could not contact Jason Cooper using current email).
- Miscellaneous changes: Move constants to .c file and remove header file
board/Marvell/dreamplug/dreamplug.h, cleanup comments.

Signed-off-by: Tony Dinh <mibodhi@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Pali Rohár <pali@kernel.org>